The Great Saint Martin Church (Groß Sankt Martin) foundations (circa 960 AD) rest on remnants of a Roman chapel, built on what was then an island in the Rhine. The church was later transformed into a Benedictine monastery.
In 1150, a fire destroyed much of Cologne and it is supposed that the entire church was destroyed. The Archbishop of Cologne Philipp I. von Heinsberg sanctified the new building in 1172, and the first phase of construction, the tri-apsidal structure was built, with three round apses meeting in the shape of a cross. This is the only element of the church still present today. The eastern end of the nave was completed before a further fire in 1185, as well as aisles on the Southside. At the northern apse, two Benedictine chapels were later added, built over the ruins of the previous abbey buildings.
In the middle of the 13th century, new walls for the three apses were completed, with larger windows. These provided a sought-after lightness to the interior. The nave was also made five meters longer, and the atrium in the west was built.
After the completion of the church in the 13th century, few modifications to the form of the church were undertaken. Most significant during this period were the various renovations needed for the four surrounding towers.
Reforms under abbots Jakob von Wachendorp (1439–1454) and Adam Meyer (1454–1499) provided a stronger financial footing for the Benedictine abbey. From this the inner decoration of the church was embellished, including figures from the altar, installed in 1509, that are still present today.
In 1707, the decaying interior walls were repaired and refurbished. Heinrich Obladen, then the abbot of Great Saint Martin, also purchased a new, larger organ for the church. New adornments for the Church took on a Baroque style, including golden bands for the pillars, dome and walls.
The church was badly damaged in World War II; restoration work was completed in 1985.References:
Frösöstenen is the northern-most raised runestone in the world and Jämtland's only runestone. It originally stood at the tip of ferry terminal on the sound between the island of Frösön and Östersund. The stone dates to between 1030 and 1050. It has now been relocated to the lawn in front of the local county seat due to the construction of a new bridge, between 1969 and 1971, on the original site.
Frösö runestone inscription means: Austmaðr, Guðfastr's son, had this stone raised and this bridge built and Christianized Jämtland. Ásbjörn built the bridge. Trjónn and Steinn carved these runes.